Checking CO2 content in auxiliary/additional heater exhaust gas — AUDI

🧭 Before you start

Fits: Audi A8 D3 (4E, 2002–2010)

• Special tools named: VAS 5051
• Renewed: if necessary

Don't miss

• Hose (B) of exhaust probe must not stop exhaust gas emerging from exhaust pipe (A) during test.
• The instantaneous operating status of the auxiliary/supplementary heater can be seen from the measured value block "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.

📋 Procedure

1. Switch on the exhaust emission test stationVAS 6300 and insert the appropriate exhaust probe hose (B) in the auxiliary/supplementary heater exhaust pipe (A). [Note: Hose (B) of exhaust probe must not stop exhaust gas emerging from exhaust pipe (A) during test.]
2. Switch on ignition (vehicles with auxiliary/additional heater).
3. Start engine (vehicles with diesel engine with additional heater only, without "“auxiliary heater”" optional extra).
4. Set maximum heat output on front operating and display unit (Climatronic control unit J255).
5. Restrict fresh-air blower speed by setting front operating and display unit to approx. 50 % of maximum fresh-air blower speed.

6. Switch on the auxiliary/supplementary heater by way of one of the two rotary knobs/pushbuttons of the front operating and display unit, Climatronic control unit J255, via the Multi Media Interface (MMI) or by way of the vehicle diagnostic, testing and information systemVAS 5051 A ("“Basic setting”" function) on vehicles with auxiliary heater Owner's manual, Operating instructions for "“Infotainment / MMI”" and "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.
7. Switch on the supplementary heater by way of the vehicle diagnostic, testing and information systemVAS 5051 A ("“Basic setting”" function) (vehicles with diesel engine with supplementary heater only - no "“Auxiliary heater”" optional extra) "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.
8. Wait until auxiliary/additional heater switches from starting to full load mode (approx. 4 minutes). [Note: The instantaneous operating status of the auxiliary/supplementary heater can be seen from the measured value block "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.]
9. Wait at least another minute after auxiliary/additional heater has switched to full load mode.
10. Read off measured value for CO2 (carbon dioxide) content in exhaust gas from CO2 measuring instrument (as of approx. 4 minutes after switch-on; auxiliary/additional heater must be in full load mode). [Note: Hose (B) of exhaust probe must not stop exhaust gas emerging from exhaust pipe (A) during test.] [Note: If measured value is in lower range (less than 9%), problems with auxiliary/additional heater combustion may be encountered under unfavourable operating conditions (e.g. high vehicle speed with auxiliary/additional heater switched on). Set CO2 content in exhaust gas to a higher value .If value displayed by CO2 measuring instrument fluctuates slightly, calculate mean value from highest and lowest measured values.If value displayed by CO2 measuring instrument fluctuates considerably (more than approx. +/- 0.6% depending on measuring instrument), check position of probe in exhaust pipe of auxiliary/additional heater.]
11. Check fresh-air intake hose with intake silencer and auxiliary/additional heater exhaust system for dirt or cross-sectional constriction and clean components concerned (replace if necessary).
12. Check fuel delivery for metering pump V54.
13. If the CO2 content of the exhaust gas and the delivery of the metering pump V54 are in the lower specified range, replace metering pump V54.
14. Check fresh-air intake hose with intake silencer and auxiliary/additional heater exhaust system for dirt or cross-sectional constriction and clean components concerned (replace if necessary).
15. Check the combustion air blower V6"Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051.
16. Adjust CO2 content in exhaust gas .
17. If CO2 content in exhaust gas cannot be adjusted, replace combustion air blower V6.
18. Check the glow plug with flame monitor Q8 and .
19. Remove any residue from auxiliary/additional heater combustion chamber (this is particularly important for vehicles with diesel engines and when running engine and thus auxiliary/additional heater on rape-oil or vegetable-oil methylester fuel)

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